Phosphors are used in fluorescent tubes, fluorescent display tubes, luminous display boards, and the like, and use of phosphors is increasing. Attempts have been made to use phosphors in combination with LEDs in various display apparatuses including TV monitors. White phosphors, which are expected to be applicable to a wide variety of fields, have also been actively studied and developed.
There are various organic and inorganic fluorescent materials, including natural fluorescent materials. In an attempt to improve required colors of light to be emitted, intensities of peaks of emission spectra, economical efficiencies, and the like, various materials have been researched and developed. In the researches and developments, there are disclosed some, but not many, boron nitride (BN) based fluorescent materials. For example, there is disclosed a method for the synthesis of a group 13 nitride, which comprises dissolving a group 13 element-containing compound and a nitrogen-containing compound in a solvent, evaporating the solvent to form a uniform mixture, and heating the uniform mixture to about 800° C. to nitride the group 13 element with nitrogen of the nitrogen-containing compound to obtain a group 13 nitride (Patent Citation 1). According to the disclosure, when fine BN particles synthesized by the above method were irradiated with ultraviolet light having a wavelength of 365 nm, a peak of an emission spectrum was observed at a wavelength of 395 nm; fine BN particles that were observed to emit light had a low degree of crystallinity (degree of hexagonal crystallinity) and contained a large amount of oxygen (11.7% by weight), whereas fine BN particles that were not observed to emit light had a high degree of crystallinity and contained a small amount of oxygen (4.1% by weight).    [Patent Citation 1] JP 2005-97022A
There is proposed a Eu2+-doped B—N—O based amorphous oxynitride phosphor having a high emission intensity at a wavelength of about 380 nm, which can efficiently excite an anatase TiO2 photocatalyst. It is disclosed that the B—N—O based amorphous oxynitride phosphors doped with Eu2+ in an amount of 1 atm % or greater had an increased emission intensity at the wavelength of 372 nm; the B—N—O based amorphous oxynitride phosphors doped with Eu2+ in an amount of 2.5 atm % or greater had a significantly increased emission intensity at the wavelength of 372 nm; and the B—N—O based amorphous oxynitride phosphor doped with Eu2+ in an amount of 5 atm % had a maximum emission intensity (Patent Citation 2).    [Patent Citation 2] JP 2005-225942A
In addition to the boron nitride based fluorescent material described above, there is disclosed a SiAlON phosphor that is obtained by firing aluminum nitride, silicon nitride, silicon oxide and rare-earth oxide, and emits visible light of various colors (Patent Citation 3).    [Patent Citation 3] JP 2008-13674A
There is also disclosed an M-Al—Si—N:Z based phosphor obtained by firing calcium nitride, aluminum nitride, silicon nitride, silicon oxide, and rare-earth oxide (Patent Citation 4).    [Patent Citation 4] JP 2006-28295A
A range of applications of such phosphors has been increasing; for example, phosphors have been applied to electroluminescent devices. There is disclosed an inorganic electroluminescent device provided with a phosphor layer having phosphor particles comprising copper-doped zinc sulfide (Patent Citation 5), an inorganic electroluminescent device comprising not only zinc sulfide but also strontium sulfide (Non Patent Citation 1), and an inorganic electroluminescent device comprising cadmium selenide and zinc oxide (Patent Citation 6). There is also disclosed an inorganic electroluminescent device comprising a compound such as barium thioaluminate (Non Patent Citation 2).    [Patent Citation 5] JP 2005-339924A    [Patent Citation 6] JP 2003-249373A    [Non Patent Citation 1] Journal of Luminescence, Volume 91, Issues 1-2, September 2000, Pages 1-6    [Non Patent Citation 2] Journal of Rare Earths, Volume 24, Issues 1, Supplement 1, December 2006, Pages 119-121